"You served on active duty. As a nation mourns McCain, it would be appropriate to lower the flag to half staff at all @StateDept buildings. I respectfully request you give that order, regardless of the views of @realDonaldTrump. It is the honorable thing to do," Lieu tweeted, sending a separate message to each Cabinet official.

Dear @SecPompeo: You served on active duty. As a nation mourns McCain, it would be appropriate to lower the flag to half staff at all @StateDept buildings. I respectfully request you give that order, regardless of the views of @realDonaldTrump. It is the honorable thing to do. https://t.co/yIllKANhMq

Dear #SecDef: You served on active duty. As a nation mourns McCain, it would be appropriate to lower the flag to half staff at all @DeptofDefense buildings. I respectfully request you give that order, regardless of the views of @realDonaldTrump. It is the honorable thing to do. https://t.co/KSHnUuYPPc

Flags at the White House returned to full staff early Monday, less than 48 hours after McCain died.

Several reporters and commentators quickly noted that flags in the past have remained lowered to honor lawmakers and major public figures until their funerals.

Joe Heim, a Washington Post reporter, posted a photo on Twitter showing that the flag outside the Department of Energy remained at half staff on Monday morning, while the flag just down the road at the Department of Agriculture was back at full staff.

Even the cabinet is closed confused about honoring McCain. Flag at Energy is half staff. At Agriculture, across the street, flag is at full staff. pic.twitter.com/gs0fr85kcr

McCain died Saturday at age 81 a little more than a year after being diagnosed with an aggressive form of brain cancer. Even after his diagnosis, he remained one of Trump's most outspoken Republican critics.

McCain reportedly did not want Trump to attend his funeral, instead requesting that former Presidents Obama and George W. Bush deliver eulogies.

During the 2016 campaign, Trump ridiculed McCain's status as a war hero. In recent months, Trump has regularly chided McCain over his decision to vote against a GOP effort to repeal the Affordable Care Act, effectively killing the measure.